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CVE-2026-27820

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 b
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:78d519e38a644bc6e1b71b060f345442573042fe62e45ab3e5a86cc165e7774e
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
1

Preserved source conflicts

No provider value was silently selected as the winner.

cwe · 2 assertions

{"cweId":"CWE-131","description":"CWE-131: Incorrect Calculation of Buffer Size","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:8aa521b159c2846baeaaa89b6678a33b60a5605d7ca6d012390e6a3333893050 · sha256:93eba853633b98a3… · /containers/cna/problemTypes/1/descriptions/0

{"cweId":"CWE-120","description":"CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:8aa521b159c2846baeaaa89b6678a33b60a5605d7ca6d012390e6a3333893050 · sha256:93eba853633b98a3… · /containers/cna/problemTypes/0/descriptions/0

Affected products and versions

1 source assertion
{"product":"zlib","vendor":"ruby","versions":[{"status":"affected","version":"< 3.0.1"},{"status":"affected","version":">= 3.1.0, < 3.1.2"},{"status":"affected","version":">= 3.2.0, < 3.2.3"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:8aa521b159c2846baeaaa89b6678a33b60a5605d7ca6d012390e6a3333893050 · sha256:93eba853633b98a3… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion
{"metric":{"attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":1.7,"baseSeverity":"LOW","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"LOW","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE"},"metric_type":"cvssV4_0"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:8aa521b159c2846baeaaa89b6678a33b60a5605d7ca6d012390e6a3333893050 · sha256:93eba853633b98a3… · /containers/cna/metrics/0/cvssV4_0

CWE assertions

2 source assertions
{"cweId":"CWE-131","description":"CWE-131: Incorrect Calculation of Buffer Size","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:8aa521b159c2846baeaaa89b6678a33b60a5605d7ca6d012390e6a3333893050 · sha256:93eba853633b98a3… · /containers/cna/problemTypes/1/descriptions/0
{"cweId":"CWE-120","description":"CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:8aa521b159c2846baeaaa89b6678a33b60a5605d7ca6d012390e6a3333893050 · sha256:93eba853633b98a3… · /containers/cna/problemTypes/0/descriptions/0

Source references

2 source assertions
{"name":"https://github.com/ruby/zlib/security/advisories/GHSA-g857-hhfv-j68w","tags":["x_refsource_CONFIRM"],"url":"https://github.com/ruby/zlib/security/advisories/GHSA-g857-hhfv-j68w"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:8aa521b159c2846baeaaa89b6678a33b60a5605d7ca6d012390e6a3333893050 · sha256:93eba853633b98a3… · /containers/cna/references/0
{"name":"https://hackerone.com/reports/3467067","tags":["x_refsource_MISC"],"url":"https://hackerone.com/reports/3467067"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:8aa521b159c2846baeaaa89b6678a33b60a5605d7ca6d012390e6a3333893050 · sha256:93eba853633b98a3… · /containers/cna/references/1

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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