CVE-2026-27820

criticalpriority · track · 39EPSS 0.006 · 46 %ileDEEURUUS
grimoire priorityP2 · Scheduled
Exploitable?
—
no known exploitation
Likely / severe?
0.56% (46th) EPSS
CVSS 9.8 · critical
Is it mine?
30 products
Check your exposure
Who says so?
6 sources
cnnvd · enisa_euvd · fstec_bdu · cert_bund

EPSS · scored 2026-10-26

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.

01

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

  • Fixedlibruby2_5-2_5-0:2.5.9-150700.24.6.1.aarch64 as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedlibruby2_5-2_5-0:2.5.9-150700.24.6.1.ppc64le as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedlibruby2_5-2_5-0:2.5.9-150700.24.6.1.s390x as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedlibruby2_5-2_5-0:2.5.9-150700.24.6.1.x86_64 as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-0:2.5.9-150700.24.6.1.aarch64 as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-0:2.5.9-150700.24.6.1.ppc64le as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-0:2.5.9-150700.24.6.1.s390x as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-0:2.5.9-150700.24.6.1.x86_64 as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-devel-0:2.5.9-150700.24.6.1.aarch64 as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-devel-0:2.5.9-150700.24.6.1.ppc64le as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-devel-0:2.5.9-150700.24.6.1.s390x as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-devel-0:2.5.9-150700.24.6.1.x86_64 as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-devel-extra-0:2.5.9-150700.24.6.1.aarch64 as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-devel-extra-0:2.5.9-150700.24.6.1.ppc64le as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-devel-extra-0:2.5.9-150700.24.6.1.s390x as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-devel-extra-0:2.5.9-150700.24.6.1.x86_64 as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-stdlib-0:2.5.9-150700.24.6.1.aarch64 as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-stdlib-0:2.5.9-150700.24.6.1.ppc64le as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-stdlib-0:2.5.9-150700.24.6.1.s390x as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

  • Fixedruby2.5-stdlib-0:2.5.9-150700.24.6.1.x86_64 as component of SUSE Linux Enterprise Module for Basesystem 15 SP7suse_csaf

    To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".

02

cvss

Technical severity, 0–10. One row per scoring source.

9.8
010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · low–critical · 1.7–9.8

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 5.9
v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · OSV
v3.18.8highAV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU
v3.18.8highCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:Hsecondary · SUSE Product Security
v4.01.7lowCVSS: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:Xsecondary · security-advisories@github.com
v4.01.7lowCVSS: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:Usecondary · ENISA EU
v4.01.7lowCVSS: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:Xsecondary · CVSS-BT (t0sche)
03

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: yes · Technical Impact: partialcoordinatorcisa_ssvcUS
04

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-120USCWE-120USCWE-120USCWE-131USCWE-131US
05

affected products (30)

Products and version ranges known to be affected.

showing 20 of 30
06

advisories (3)

Vendor and ecosystem advisories describing this.

  • SUSE-SU-2026:1066-1Security update for ruby2.52026-03-26csaf · suse_csafDE

    Security update for ruby2.5

  • WID-SEC-W-2026-0595Ruby: Schwachstelle ermöglicht Denial of ServiceDeutsch2026-03-04csaf · cert_bundDE

    Ein lokaler Angreifer kann eine Schwachstelle in Ruby ausnutzen, um einen Denial of Service Angriff durchzuführen.

  • GHSA-g857-hhfv-j68wBuffer Overflow in Zlib::GzipReader ungetc via large input leads to memory corruption2026-04-16ghsa · osvUS

    ### Details A buffer overflow vulnerability exists in `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. ### Recommended action We recommend to update the `zlib` gem to version 3.2.3 or later. In order to ensure compatibility with bundled version in older Ruby series, you may update as follows instead: * For Ruby 3.2 users: Update to zlib 3.0.1 * For Ruby 3.3 users: Update to zlib 3.1.2 You can use gem update zlib to update it. If you are using bundler, please add `gem "zlib", ">= 3.2.3"` to your Gemfile. ### Affected versions zlib gem 3.2.2 or lower ### Credits [calysteon](https://hackerone.com/calysteon) ### References * https://hackerone.com/reports/3467067

07

also known as (3)

Other names and identifiers for this entity.

08

sources

Which sources assert this record, and when.

cnnvdenisa_euvdfstec_bducert_bundsuse_csafosvNVDCVE.orgMITRE
published 2026-04-16modified 2026-10-26
09

references (8)

External citations — patches, advisories, analysis.

scry

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