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CVE-2026-98955

CVE-2026-98955 · flow_dissector: avoid u16 truncation of skb->len when computing thoff

This page contains facts from public vulnerability sources. Check the original advisory before updating.

In the Linux kernel, the following vulnerability has been resolved: flow_dissector: avoid u16 truncation of skb->len when computing thoff __skb_flow_dissect() computes key_control->thoff using: key_control->thoff = min_t(u16, nhoff, skb ? skb->len : hlen); min_t(u16, ...) casts both arguments to u16 before comparing them. Whenever skb->len (or hlen) modulo 65536 is smaller than nhoff, the truncated length wins and thoff is set to a bogus small value, even when the dissection succeeded. For example, an IPv4/TCP frame with skb->len == 65540 and nhoff == 34 gets thoff == 4, so callers such as skb_probe_transport_header() point the transport header inside the Ethernet header. Such skbs are not exotic: - At the time of commit d0c081b49137 ("flow_dissector: properly cap thoff field"), AF_PACKET with PACKET_VNET_HDR could already build GSO skbs larger than 64KB (MTU checks are skipped for GSO, and alloc_skb_with_frags() accepted up to MAX_SKB_FRAGS (17) order-0 pages on top of the linear part). - BIG TCP now makes skbs larger than 64KB common. - The following patch makes tun_get_user() dissect IFF_TAP frames before eth_type_trans() pulls the Ethernet header, so a GSO frame carrying a 65522..65535 byte L3 packet will be dissected with skb->len in [65536, 65549]. Compare as u32 instead. If the resulting offset cannot be represented in the u16 key_control->thoff, cap it to U16_MAX and report the dissection as failed rather than silently returning a wrong transport offset. thoff is still set on failure, as some callers (such as eth_get_headlen()) use it regardless of the return value.

Fix available

Published
Updated

Stack: system

Affected products and versions

  • linux

    Versions
    • ≥ d0c081b49137cd3200f2023c0875723be66e7ce5, < d9e08836d06c84abb18470c94b12b131eaccdc7d: Affected (git)
    • ≥ d0c081b49137cd3200f2023c0875723be66e7ce5, < 50d0cd575cab763f833d6ac6eb6550b23a0b3dae: Affected (git)
    • ≥ d0c081b49137cd3200f2023c0875723be66e7ce5, < 9993e6a0ac1b5b3101ffba702cacb9f42b9909d8: Affected (git)
    • ≥ d0c081b49137cd3200f2023c0875723be66e7ce5, < 52efce4755a4b8b82039caa773645ffc80b25362: Affected (git)
    • ≥ d0c081b49137cd3200f2023c0875723be66e7ce5, < 99bda1ecbd56905f8bd934b9cdccd3bd251192b1: Affected (git)
    • d35cd5e279881ec36ff8cd82a2d9caebc0cce3fc: Affected (git)
    • eecfa2eeefe3caef4c8d6b2284f6066c76ab26a1: Affected (git)
    • 80f327285cab6ab8e10c3ea03278add5dd99fb02: Affected (git)
    • ≥ 4.4.114, < 4.5: Affected (semver)
    • ≥ 4.9.79, < 4.10: Affected (semver)
    • ≥ 4.14.16, < 4.15: Affected (semver)

    Update to 50d0cd575cab763f833d6ac6eb6550b23a0b3dae; Update to 9993e6a0ac1b5b3101ffba702cacb9f42b9909d8; Update to d9e08836d06c84abb18470c94b12b131eaccdc7d

  • linux

    Versions
    • 4.15: Affected
    • ≥ 0, < 4.15: Not affected (semver)
    • ≥ 6.6.160, ≤ 6.6.*: Not affected (semver)
    • ≥ 6.12.113, ≤ 6.12.*: Not affected (semver)
    • ≥ 6.18.57, ≤ 6.18.*: Not affected (semver)
    • ≥ 7.2.11, ≤ 7.2.*: Not affected (semver)
    • ≥ 7.3: Not affected (original_commit_for_fix)

    No fix published

  • linux Debian:12

    Versions
    • 6.1.106-1
    • 6.1.106-2
    • 6.1.106-3
    • 6.1.112-1
    • 6.1.115-1
    • 6.1.119-1
    • 6.1.123-1
    • 6.1.124-1
    • 6.1.128-1
    • 6.1.129-1
    • 6.1.133-1
    • 6.1.135-1
    • 6.1.137-1
    • 6.1.139-1
    • 6.1.140-1
    • 6.1.147-1
    • 6.1.148-1
    • 6.1.153-1
    • 6.1.158-1
    • 6.1.159-1
    • 6.1.162-1
    • 6.1.164-1
    • 6.1.170-1
    • 6.1.170-2
    • 6.1.170-3
    • 6.1.172-1
    • 6.1.174-1
    • 6.1.176-1
    • 6.1.177-1
    • 6.1.180-1
    • 6.1.187-1
    • 6.1.190-1
    • 6.1.27-1
    • 6.1.37-1
    • 6.1.38-1
    • 6.1.38-2
    • 6.1.38-2~bpo11+1
    • 6.1.38-3
    • 6.1.38-4
    • 6.1.38-4~bpo11+1
    • 6.1.52-1
    • 6.1.55-1
    • 6.1.55-1~bpo11+1
    • 6.1.64-1
    • 6.1.66-1
    • 6.1.67-1
    • 6.1.69-1
    • 6.1.69-1~bpo11+1
    • 6.1.76-1
    • 6.1.76-1~bpo11+1
    • 6.1.82-1
    • 6.1.85-1
    • 6.1.90-1
    • 6.1.90-1~bpo11+1
    • 6.1.94-1
    • 6.1.94-1~bpo11+1
    • 6.1.98-1
    • 6.1.99-1
    • 6.10-1~exp1
    • 6.10.1-1~exp1
    • 6.10.11-1
    • 6.10.11-1~bpo12+1
    • 6.10.12-1
    • 6.10.3-1
    • 6.10.4-1
    • 6.10.6-1
    • 6.10.6-1~bpo12+1
    • 6.10.7-1
    • 6.10.9-1
    • 6.11-1~exp1
    • 6.11.10-1
    • 6.11.10-1~bpo12+1
    • 6.11.2-1
    • 6.11.4-1
    • 6.11.5-1
    • 6.11.5-1~bpo12+1
    • 6.11.6-1
    • 6.11.7-1
    • 6.11.9-1
    • 6.11~rc4-1~exp1
    • 6.11~rc5-1~exp1
    • 6.12.10-1
    • 6.12.100-1
    • 6.12.101-1
    • 6.12.105-1
    • 6.12.107-1
    • 6.12.11-1
    • 6.12.11-1+alpha
    • 6.12.11-1+alpha.1
    • 6.12.111-1
    • 6.12.113-1
    • 6.12.12-1
    • 6.12.12-1~bpo12+1
    • 6.12.13-1
    • 6.12.15-1
    • 6.12.16-1
    • 6.12.17-1
    • 6.12.19-1
    • 6.12.20-1
    • 6.12.21-1
    • 6.12.22-1
    • 6.12.22-1~bpo12+1
    • 6.12.25-1
    • 6.12.27-1
    • 6.12.27-1~bpo12+1
    • 6.12.29-1
    • 6.12.3-1
    • 6.12.30-1
    • 6.12.30-1~bpo12+1
    • 6.12.31-1
    • 6.12.32-1
    • 6.12.32-1~bpo12+1
    • 6.12.33-1
    • 6.12.33-1~bpo12+1
    • 6.12.35-1
    • 6.12.35-1~bpo12+1
    • 6.12.37-1
    • 6.12.38-1
    • 6.12.38-1~bpo12+1
    • 6.12.41-1
    • 6.12.43-1
    • 6.12.43-1~bpo12+1
    • 6.12.48-1
    • 6.12.5-1
    • 6.12.57-1
    • 6.12.57-1~bpo12+1
    • 6.12.6-1
    • 6.12.63-1
    • 6.12.63-1~bpo12+1
    • 6.12.69-1
    • 6.12.69-1~bpo12+1
    • 6.12.73-1
    • 6.12.73-1~bpo12+1
    • 6.12.74-1
    • 6.12.74-2
    • 6.12.74-2~bpo12+1
    • 6.12.8-1
    • 6.12.85-1
    • 6.12.85-1~bpo12+1
    • 6.12.86-1
    • 6.12.86-1~bpo12+1
    • 6.12.88-1
    • 6.12.88-1~bpo12+1
    • 6.12.9-1
    • 6.12.9-1+alpha
    • 6.12.9-1~bpo12+1
    • 6.12.90-1
    • 6.12.90-1~bpo12+1
    • 6.12.90-2
    • 6.12.90-2~bpo12+1
    • 6.12.94-1
    • 6.12.94-1~bpo12+1
    • 6.12.95-1
    • 6.12.95-1~bpo12+1
    • 6.12.96-1
    • 6.12~rc6-1~exp1
    • 6.13.10-1~exp1
    • 6.13.11-1~exp1
    • 6.13.2-1~exp1
    • 6.13.3-1~exp1
    • 6.13.4-1~exp1
    • 6.13.5-1~exp1
    • 6.13.6-1~exp1
    • 6.13.7-1~exp1
    • 6.13.8-1~exp1
    • 6.13.9-1~exp1
    • 6.13~rc6-1~exp1
    • 6.13~rc7-1~exp1
    • 6.14.3-1~exp1
    • 6.14.5-1~exp1
    • 6.14.6-1~exp1
    • 6.15-1~exp1
    • 6.15.1-1~exp1
    • 6.15.2-1~exp1
    • 6.15.3-1~exp1
    • 6.15.4-1~exp1
    • 6.15.5-1~exp1
    • 6.15.6-1~exp1
    • 6.15~rc7-1~exp1
    • 6.16-1~exp1
    • 6.16.1-1~exp1
    • 6.16.10-1
    • 6.16.11-1
    • 6.16.12-1
    • 6.16.12-1~bpo13+1
    • 6.16.12-2
    • 6.16.3-1
    • 6.16.3-1~bpo13+1
    • 6.16.5-1
    • 6.16.6-1
    • 6.16.7-1
    • 6.16.8-1
    • 6.16.9-1
    • 6.16~rc7-1~exp1
    • 6.17.10-1
    • 6.17.11-1
    • 6.17.12-1
    • 6.17.13-1
    • 6.17.13-1~bpo13+1
    • 6.17.2-1~exp1
    • 6.17.5-1~exp1
    • 6.17.6-1
    • 6.17.7-1
    • 6.17.7-2
    • 6.17.8-1
    • 6.17.8-1~bpo13+1
    • 6.17.9-1
    • 6.18.1-1~exp1
    • 6.18.10-1
    • 6.18.12-1
    • 6.18.12-1~bpo13+1
    • 6.18.13-1
    • 6.18.14-1
    • 6.18.15-1
    • 6.18.15-1~bpo13+1
    • 6.18.2-1~exp1
    • 6.18.3-1
    • 6.18.5-1
    • 6.18.5-1~bpo13+1
    • 6.18.8-1
    • 6.18.9-1
    • 6.18.9-1~bpo13+1
    • 6.18~rc4-1~exp1
    • 6.18~rc4-1~exp2
    • 6.18~rc5-1~exp1
    • 6.18~rc6-1~exp1
    • 6.18~rc7-1~exp1
    • 6.19-1~exp1
    • 6.19.10-1
    • 6.19.10-1~bpo13+1
    • 6.19.11-1
    • 6.19.11-1~bpo13+1
    • 6.19.12-1
    • 6.19.13-1
    • 6.19.13-1~bpo13+1
    • 6.19.14-1
    • 6.19.14-1~bpo13+1
    • 6.19.2-1~exp1
    • 6.19.3-1~exp1
    • 6.19.4-1~exp1
    • 6.19.5-1~exp1
    • 6.19.6-1
    • 6.19.6-2
    • 6.19.6-2~bpo13+1
    • 6.19.8-1
    • 6.19.8-1~bpo13+1
    • 6.19~rc4-1~exp1
    • 6.19~rc5-1~exp1
    • 6.19~rc6-1~exp1
    • 6.19~rc7-1~exp1
    • 6.19~rc8-1~exp1
    • 6.3.1-1~exp1
    • 6.3.11-1
    • 6.3.2-1~exp1
    • 6.3.4-1~exp1
    • 6.3.5-1~exp1
    • 6.3.7-1
    • 6.3.7-1~bpo12+1
    • 6.4.1-1~exp1
    • 6.4.11-1
    • 6.4.13-1
    • 6.4.4-1
    • 6.4.4-1~bpo12+1
    • 6.4.4-2
    • 6.4.4-3
    • 6.4.4-3~bpo12+1
    • 6.4~rc6-1~exp1
    • 6.4~rc7-1~exp1
    • 6.5.1-1~exp1
    • 6.5.10-1
    • 6.5.10-1~bpo12+1
    • 6.5.13-1
    • 6.5.3-1
    • 6.5.3-1~bpo12+1
    • 6.5.6-1
    • 6.5.8-1
    • 6.5~rc4-1~exp1
    • 6.5~rc6-1~exp1
    • 6.5~rc7-1~exp1
    • 6.6.11-1
    • 6.6.13-1
    • 6.6.13-1~bpo12+1
    • 6.6.15-1
    • 6.6.15-2
    • 6.6.3-1~exp1
    • 6.6.4-1~exp1
    • 6.6.7-1~exp1
    • 6.6.8-1
    • 6.6.9-1
    • 6.7-1~exp1
    • 6.7.1-1~exp1
    • 6.7.12-1
    • 6.7.12-1~bpo12+1
    • 6.7.4-1~exp1
    • 6.7.7-1
    • 6.7.9-1
    • 6.7.9-2
    • 6.8.11-1
    • 6.8.12-1
    • 6.8.12-1~bpo12+1
    • 6.8.9-1
    • 6.9.10-1
    • 6.9.10-1~bpo12+1
    • 6.9.11-1
    • 6.9.12-1
    • 6.9.2-1~exp1
    • 6.9.7-1
    • 6.9.7-1~bpo12+1
    • 6.9.8-1
    • 6.9.9-1
    • 7.0-1~exp1
    • 7.0.1-1~exp1
    • 7.0.10-1
    • 7.0.10-1~bpo13+1
    • 7.0.12-1
    • 7.0.12-2
    • 7.0.12-2~bpo13+1
    • 7.0.13-1
    • 7.0.13-1~bpo13+1
    • 7.0.14-1
    • 7.0.3-1
    • 7.0.4-1
    • 7.0.4-1~bpo13+1
    • 7.0.7-1
    • 7.0.7-1~bpo13+1
    • 7.0.9-1
    • 7.0.9-1~bpo13+1
    • 7.1.1-1~exp1
    • 7.1.10-1
    • 7.1.12-1
    • 7.1.13-1
    • 7.1.13-1~bpo13+1
    • 7.1.2-1~exp1
    • 7.1.3-1
    • 7.1.3-1+sunvdc
    • 7.1.3-1~bpo13+1
    • 7.1.4-1
    • 7.1.5-1
    • 7.1.6-1
    • 7.1.7-1
    • 7.1.7-1~bpo13+1
    • 7.1.8-1
    • 7.1.8-1~bpo13+1
    • 7.1.8-2
    • 7.1.9-1
    • 7.1.9-1+sparc64
    • 7.1~rc2-1~exp1
    • 7.1~rc3-1~exp1
    • 7.1~rc4-1~exp1
    • 7.1~rc4-1~exp2
    • 7.1~rc5-1~exp1
    • 7.1~rc7-1~exp1
    • 7.2.10-1
    • 7.2.11-1
    • 7.2.12-1
    • 7.2.2-1~exp1
    • 7.2.3-1~exp1
    • 7.2.6-1
    • 7.2.6-1~bpo13+1
    • 7.2.7-1
    • 7.2.8-1
    • 7.2.9-1
    • 7.2.9-1~bpo13+1
    • 7.2~rc3-1~exp1
    • 7.2~rc5-1~exp1
    • 7.2~rc7-1~exp1
    • 7.3~rc6-1~exp1
    • 7.3~rc7-1~exp1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • linux Debian:13

    Versions
    • 6.12.100-1
    • 6.12.101-1
    • 6.12.105-1
    • 6.12.107-1
    • 6.12.111-1
    • 6.12.38-1
    • 6.12.41-1
    • 6.12.43-1
    • 6.12.43-1~bpo12+1
    • 6.12.48-1
    • 6.12.57-1
    • 6.12.57-1~bpo12+1
    • 6.12.63-1
    • 6.12.63-1~bpo12+1
    • 6.12.69-1
    • 6.12.69-1~bpo12+1
    • 6.12.73-1
    • 6.12.73-1~bpo12+1
    • 6.12.74-1
    • 6.12.74-2
    • 6.12.74-2~bpo12+1
    • 6.12.85-1
    • 6.12.85-1~bpo12+1
    • 6.12.86-1
    • 6.12.86-1~bpo12+1
    • 6.12.88-1
    • 6.12.88-1~bpo12+1
    • 6.12.90-1
    • 6.12.90-1~bpo12+1
    • 6.12.90-2
    • 6.12.90-2~bpo12+1
    • 6.12.94-1
    • 6.12.94-1~bpo12+1
    • 6.12.95-1
    • 6.12.95-1~bpo12+1
    • 6.12.96-1
    Affected ranges
    • ECOSYSTEM: < 6.12.113-1

    Update to 6.12.113-1

  • linux Debian:14

    Versions
    • 6.12.100-1
    • 6.12.101-1
    • 6.12.105-1
    • 6.12.107-1
    • 6.12.111-1
    • 6.12.113-1
    • 6.12.38-1
    • 6.12.41-1
    • 6.12.43-1
    • 6.12.43-1~bpo12+1
    • 6.12.48-1
    • 6.12.57-1
    • 6.12.57-1~bpo12+1
    • 6.12.63-1
    • 6.12.63-1~bpo12+1
    • 6.12.69-1
    • 6.12.69-1~bpo12+1
    • 6.12.73-1
    • 6.12.73-1~bpo12+1
    • 6.12.74-1
    • 6.12.74-2
    • 6.12.74-2~bpo12+1
    • 6.12.85-1
    • 6.12.85-1~bpo12+1
    • 6.12.86-1
    • 6.12.86-1~bpo12+1
    • 6.12.88-1
    • 6.12.88-1~bpo12+1
    • 6.12.90-1
    • 6.12.90-1~bpo12+1
    • 6.12.90-2
    • 6.12.90-2~bpo12+1
    • 6.12.94-1
    • 6.12.94-1~bpo12+1
    • 6.12.95-1
    • 6.12.95-1~bpo12+1
    • 6.12.96-1
    • 6.13.10-1~exp1
    • 6.13.11-1~exp1
    • 6.13.2-1~exp1
    • 6.13.3-1~exp1
    • 6.13.4-1~exp1
    • 6.13.5-1~exp1
    • 6.13.6-1~exp1
    • 6.13.7-1~exp1
    • 6.13.8-1~exp1
    • 6.13.9-1~exp1
    • 6.13~rc6-1~exp1
    • 6.13~rc7-1~exp1
    • 6.14.3-1~exp1
    • 6.14.5-1~exp1
    • 6.14.6-1~exp1
    • 6.15-1~exp1
    • 6.15.1-1~exp1
    • 6.15.2-1~exp1
    • 6.15.3-1~exp1
    • 6.15.4-1~exp1
    • 6.15.5-1~exp1
    • 6.15.6-1~exp1
    • 6.15~rc7-1~exp1
    • 6.16-1~exp1
    • 6.16.1-1~exp1
    • 6.16.10-1
    • 6.16.11-1
    • 6.16.12-1
    • 6.16.12-1~bpo13+1
    • 6.16.12-2
    • 6.16.3-1
    • 6.16.3-1~bpo13+1
    • 6.16.5-1
    • 6.16.6-1
    • 6.16.7-1
    • 6.16.8-1
    • 6.16.9-1
    • 6.16~rc7-1~exp1
    • 6.17.10-1
    • 6.17.11-1
    • 6.17.12-1
    • 6.17.13-1
    • 6.17.13-1~bpo13+1
    • 6.17.2-1~exp1
    • 6.17.5-1~exp1
    • 6.17.6-1
    • 6.17.7-1
    • 6.17.7-2
    • 6.17.8-1
    • 6.17.8-1~bpo13+1
    • 6.17.9-1
    • 6.18.1-1~exp1
    • 6.18.10-1
    • 6.18.12-1
    • 6.18.12-1~bpo13+1
    • 6.18.13-1
    • 6.18.14-1
    • 6.18.15-1
    • 6.18.15-1~bpo13+1
    • 6.18.2-1~exp1
    • 6.18.3-1
    • 6.18.5-1
    • 6.18.5-1~bpo13+1
    • 6.18.8-1
    • 6.18.9-1
    • 6.18.9-1~bpo13+1
    • 6.18~rc4-1~exp1
    • 6.18~rc4-1~exp2
    • 6.18~rc5-1~exp1
    • 6.18~rc6-1~exp1
    • 6.18~rc7-1~exp1
    • 6.19-1~exp1
    • 6.19.10-1
    • 6.19.10-1~bpo13+1
    • 6.19.11-1
    • 6.19.11-1~bpo13+1
    • 6.19.12-1
    • 6.19.13-1
    • 6.19.13-1~bpo13+1
    • 6.19.14-1
    • 6.19.14-1~bpo13+1
    • 6.19.2-1~exp1
    • 6.19.3-1~exp1
    • 6.19.4-1~exp1
    • 6.19.5-1~exp1
    • 6.19.6-1
    • 6.19.6-2
    • 6.19.6-2~bpo13+1
    • 6.19.8-1
    • 6.19.8-1~bpo13+1
    • 6.19~rc4-1~exp1
    • 6.19~rc5-1~exp1
    • 6.19~rc6-1~exp1
    • 6.19~rc7-1~exp1
    • 6.19~rc8-1~exp1
    • 7.0-1~exp1
    • 7.0.1-1~exp1
    • 7.0.10-1
    • 7.0.10-1~bpo13+1
    • 7.0.12-1
    • 7.0.12-2
    • 7.0.12-2~bpo13+1
    • 7.0.13-1
    • 7.0.13-1~bpo13+1
    • 7.0.14-1
    • 7.0.3-1
    • 7.0.4-1
    • 7.0.4-1~bpo13+1
    • 7.0.7-1
    • 7.0.7-1~bpo13+1
    • 7.0.9-1
    • 7.0.9-1~bpo13+1
    • 7.1.1-1~exp1
    • 7.1.10-1
    • 7.1.12-1
    • 7.1.13-1
    • 7.1.13-1~bpo13+1
    • 7.1.2-1~exp1
    • 7.1.3-1
    • 7.1.3-1+sunvdc
    • 7.1.3-1~bpo13+1
    • 7.1.4-1
    • 7.1.5-1
    • 7.1.6-1
    • 7.1.7-1
    • 7.1.7-1~bpo13+1
    • 7.1.8-1
    • 7.1.8-1~bpo13+1
    • 7.1.8-2
    • 7.1.9-1
    • 7.1.9-1+sparc64
    • 7.1~rc2-1~exp1
    • 7.1~rc3-1~exp1
    • 7.1~rc4-1~exp1
    • 7.1~rc4-1~exp2
    • 7.1~rc5-1~exp1
    • 7.1~rc7-1~exp1
    • 7.2.10-1
    • 7.2.2-1~exp1
    • 7.2.3-1~exp1
    • 7.2.6-1
    • 7.2.6-1~bpo13+1
    • 7.2.7-1
    • 7.2.8-1
    • 7.2.9-1
    • 7.2.9-1~bpo13+1
    • 7.2~rc3-1~exp1
    • 7.2~rc5-1~exp1
    • 7.2~rc7-1~exp1
    Affected ranges
    • ECOSYSTEM: < 7.2.11-1

    Update to 7.2.11-1

Original sources

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