CVE-2026-27820
CVE-2026-27820 · zlib: Buffer Overflow in Zlib::GzipReader ungetc via large input leads to memory corruption
This page contains facts from public vulnerability sources. Check the original advisory before updating.
zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.
CVSS 1.7 · Low · EPSS 0.6% · Fix available
- Published
- Updated
Stack: system
Affected products and versions
zlib
- Versions
- < 3.0.1: Affected
- >= 3.1.0, < 3.1.2: Affected
- >= 3.2.0, < 3.2.3: Affected
No fix published
ruby3.1 Debian:12
- Versions
- 3.1.2-7
- 3.1.2-7+deb12u1
- 3.1.2-7+hurd.1
- 3.1.2-8
- 3.1.2-8.1~exp1
- 3.1.2-8.3
- 3.1.2-8.4
- 3.1.2-8.5
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
ruby3.3 Debian:13
- Versions
- 3.3.8-2
- 3.3.8-2.1
- 3.3.8-2.2
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
ruby3.3 Debian:14
- Versions
- 3.3.8-2
- 3.3.8-2.1
- 3.3.8-2.2
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
jruby Ubuntu:Pro:14.04:LTS
- Versions
- 1.5.6-5ubuntu1
- 1.5.6-6
- 1.5.6-7
- 1.5.6-9+deb8u2build0.14.04.1~esm2
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
ruby2.3 Ubuntu:Pro:16.04:LTS
- Versions
- 2.3.0-1
- 2.3.0-2
- 2.3.0-4ubuntu2
- 2.3.0-4ubuntu3
- 2.3.0-5ubuntu1
- 2.3.1-2~16.04
- 2.3.1-2~16.04.2
- 2.3.1-2~16.04.4
- 2.3.1-2~16.04.5
- 2.3.1-2~16.04.6
- 2.3.1-2~16.04.7
- 2.3.1-2~16.04.9
- 2.3.1-2~16.04.10
- 2.3.1-2~16.04.11
- 2.3.1-2~16.04.12
- 2.3.1-2~ubuntu16.04.13
- 2.3.1-2~ubuntu16.04.14
- 2.3.1-2~ubuntu16.04.15
- 2.3.1-2~ubuntu16.04.16
- 2.3.1-2~ubuntu16.04.16+esm1
- 2.3.1-2~ubuntu16.04.16+esm2
- 2.3.1-2~ubuntu16.04.16+esm3
- 2.3.1-2~ubuntu16.04.16+esm4
- 2.3.1-2~ubuntu16.04.16+esm5
- 2.3.1-2~ubuntu16.04.16+esm6
- 2.3.1-2~ubuntu16.04.16+esm7
- 2.3.1-2~ubuntu16.04.16+esm8
- 2.3.1-2~ubuntu16.04.16+esm9
- 2.3.1-2~ubuntu16.04.16+esm10
- 2.3.1-2~ubuntu16.04.16+esm11
- 2.3.1-2~ubuntu16.04.16+esm12
- 2.3.1-2~ubuntu16.04.16+esm14
- Affected ranges
- ECOSYSTEM: < 2.3.1-2~ubuntu16.04.16+esm15
Update to 2.3.1-2~ubuntu16.04.16+esm15
jruby Ubuntu:16.04:LTS
- Versions
- 1.7.21-2ubuntu4
- 1.7.22-1ubuntu1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
ruby2.5 Ubuntu:Pro:18.04:LTS
- Versions
- 2.5.0~preview1-1ubuntu2
- 2.5.0-4ubuntu1
- 2.5.0-4ubuntu4
- 2.5.0-5ubuntu1
- 2.5.0-6ubuntu1
- 2.5.1-1ubuntu1
- 2.5.1-1ubuntu1.1
- 2.5.1-1ubuntu1.2
- 2.5.1-1ubuntu1.4
- 2.5.1-1ubuntu1.5
- 2.5.1-1ubuntu1.6
- 2.5.1-1ubuntu1.7
- 2.5.1-1ubuntu1.8
- 2.5.1-1ubuntu1.9
- 2.5.1-1ubuntu1.10
- 2.5.1-1ubuntu1.11
- 2.5.1-1ubuntu1.12
- 2.5.1-1ubuntu1.13
- 2.5.1-1ubuntu1.14
- 2.5.1-1ubuntu1.15
- 2.5.1-1ubuntu1.16
- 2.5.1-1ubuntu1.16+esm1
- 2.5.1-1ubuntu1.16+esm3
- 2.5.1-1ubuntu1.16+esm4
- 2.5.1-1ubuntu1.16+esm5
- 2.5.1-1ubuntu1.16+esm6
- 2.5.1-1ubuntu1.16+esm7
- 2.5.1-1ubuntu1.16+esm8
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
jruby Ubuntu:18.04:LTS
- Versions
- 9.1.13.0-1
- 9.1.17.0-1~18.04
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
ruby2.7 Ubuntu:Pro:20.04:LTS
- Versions
- 2.7.0-1
- 2.7.0-2
- 2.7.0-3
- 2.7.0-4
- 2.7.0-4ubuntu1
- 2.7.0-5ubuntu1
- 2.7.0-5ubuntu1.1
- 2.7.0-5ubuntu1.2
- 2.7.0-5ubuntu1.3
- 2.7.0-5ubuntu1.4
- 2.7.0-5ubuntu1.5
- 2.7.0-5ubuntu1.6
- 2.7.0-5ubuntu1.7
- 2.7.0-5ubuntu1.8
- 2.7.0-5ubuntu1.9
- 2.7.0-5ubuntu1.10
- 2.7.0-5ubuntu1.11
- 2.7.0-5ubuntu1.12
- 2.7.0-5ubuntu1.13
- 2.7.0-5ubuntu1.14
- 2.7.0-5ubuntu1.15
- 2.7.0-5ubuntu1.16
- 2.7.0-5ubuntu1.17
- 2.7.0-5ubuntu1.18
- 2.7.0-5ubuntu1.18+esm1
- 2.7.0-5ubuntu1.18+esm3
- 2.7.0-5ubuntu1.18+esm4
- 2.7.0-5ubuntu1.18+esm5
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
jruby Ubuntu:20.04:LTS
- Versions
- 9.1.17.0-3
- 9.1.17.0-3build5
- 9.1.17.0-3build6
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
ruby3.0 Ubuntu:22.04:LTS
- Versions
- 3.0.2-5ubuntu1
- 3.0.2-7
- 3.0.2-7ubuntu2
- 3.0.2-7ubuntu2.1
- 3.0.2-7ubuntu2.2
- 3.0.2-7ubuntu2.3
- 3.0.2-7ubuntu2.4
- 3.0.2-7ubuntu2.5
- 3.0.2-7ubuntu2.6
- 3.0.2-7ubuntu2.7
- 3.0.2-7ubuntu2.8
- 3.0.2-7ubuntu2.10
- 3.0.2-7ubuntu2.11
- 3.0.2-7ubuntu2.12
- 3.0.2-7ubuntu2.13
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
jruby Ubuntu:24.04:LTS
- Versions
- 9.3.9.0+ds-1
- 9.4.5.0+ds-1
- 9.4.5.0+ds-1ubuntu1
- 9.4.6.0+ds-1ubuntu3
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
ruby3.2 Ubuntu:24.04:LTS
- Versions
- 3.2.3-1
- 3.2.3-1build2
- 3.2.3-1build3
- 3.2.3-1ubuntu0.24.04.1
- 3.2.3-1ubuntu0.24.04.3
- 3.2.3-1ubuntu0.24.04.5
- 3.2.3-1ubuntu0.24.04.6
- 3.2.3-1ubuntu0.24.04.7
- 3.2.3-1ubuntu0.24.04.8
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
jruby Ubuntu:25.10
- Versions
- 9.4.8.0+ds-2ubuntu1
- 9.4.8.0+ds-3ubuntu1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
ruby3.3 Ubuntu:25.10
- Versions
- 3.3.7-1ubuntu2
- 3.3.8-2ubuntu1
- 3.3.8-2ubuntu2
- 3.3.8-2ubuntu2.1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
jruby Ubuntu:26.10
- Versions
- 9.4.8.0+ds-3ubuntu1
- 9.4.14.0+ds-1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
ruby3.3 Ubuntu:26.10
- Versions
- 3.3.8-2ubuntu3
- 3.3.8-2.2ubuntu4
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
jruby Ubuntu:26.04:LTS
- Versions
- 9.4.8.0+ds-3ubuntu1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
ruby3.3 Ubuntu:26.04:LTS
- Versions
- 3.3.8-2ubuntu2
- 3.3.8-2ubuntu3
- 3.3.8-2ubuntu3.1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published