zlib: Buffer Overflow in Zlib::GzipReader ungetc via large input leads to memory corruption (ruby zlib)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.56 % · percentile 47 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Analyzed
Description
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.
Weaknesses (CWE)
- CWE-120 — Buffer Copy without Checking Size of Input
- CWE-131 — Incorrect Calculation of Buffer Size
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 4.0 | LOW 1.7 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U | GitHub_M |
| CVSS 4.0 | LOW 1.7 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X | NVD · security-advisories@github.com (Secondary) |
| CVSS 3.1 | CRITICAL 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H | NVD · nvd@nist.gov (Primary) |
Advisories
- GHSA-g857-hhfv-j68w — Buffer Overflow in Zlib::GzipReader ungetc via large input leads to memory corruption
European references
- ENISA EUVD · EUVD-2026-23278
- GCVE · GCVE-0-2026-27820
CERT-FR advisories
- CERTFR-2026-AVI-0519 — Multiples vulnérabilités dans Microsoft Azure Linux · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:ruby-lang:zlib:*:*:*:*:*:ruby:*:*< 3.0.1cpe:2.3:a:ruby-lang:zlib:*:*:*:*:*:ruby:*:*≥ 3.1.0 < 3.1.2cpe:2.3:a:ruby-lang:zlib:*:*:*:*:*:ruby:*:*≥ 3.2.0 < 3.2.3
Affected products
| Product | Versions |
|---|---|
| ruby · zlib | affected < 3.0.1 ; affected >= 3.1.0, < 3.1.2 ; affected >= 3.2.0, < 3.2.3 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |