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CVE-2021-43535 (GCVE-0-2021-43535)

Vulnerability from cvelistv5 – Published: 2021-12-08 21:20 – Updated: 2024-08-04 03:55
VLAI
Summary
A use-after-free could have occured when an HTTP2 session object was released on a different thread, leading to memory corruption and a potentially exploitable crash. This vulnerability affects Firefox < 93, Thunderbird < 91.3, and Firefox ESR < 91.3.
Severity
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE
  • Use-after-free in HTTP2 Session object
Assigner
References
Impacted products
Vendor Product Version CPE status
Mozilla Firefox Affected: unspecified , < 93 (custom)
guessed Create a notification for this product.
Mozilla Thunderbird Affected: unspecified , < 91.3 (custom)
guessed Create a notification for this product.
Mozilla Firefox ESR Affected: unspecified , < 91.3 (custom)
guessed Create a notification for this product.
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Advisory\"]},{\"url\":\"https://www.mozilla.org/security/advisories/mfsa2021-50/\",\"source\":\"security@mozilla.org\",\"tags\":[\"Vendor Advisory\"]},{\"url\":\"https://bugzilla.mozilla.org/show_bug.cgi?id=1667102\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Issue Tracking\",\"Permissions Required\",\"Vendor Advisory\"]},{\"url\":\"https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Mailing List\",\"Third Party Advisory\"]},{\"url\":\"https://www.debian.org/security/2021/dsa-5026\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Third Party Advisory\"]},{\"url\":\"https://www.debian.org/security/2022/dsa-5034\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Issue Tracking\",\"Third Party Advisory\"]},{\"url\":\"https://www.mozilla.org/security/advisories/mfsa2021-43/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Vendor Advisory\"]},{\"url\":\"https://www.mozilla.org/security/advisories/mfsa2021-49/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Vendor Advisory\"]},{\"url\":\"https://www.mozilla.org/security/advisories/mfsa2021-50/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Vendor Advisory\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2025-11-21T14:53:49+00:00",
      "cve": "CVE-2021-43535",
      "id": "CVE-2021-43535",
      "initial_release_date": "2021-11-02T00:00:00+00:00",
      "product_status:fixed": "144",
      "product_status:known_affected": "4",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "Mozilla: Use-after-free in HTTP2 Session object",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-43535.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-02T02:21:55Z",
      "cve": "CVE-2021-43535",
      "id": "CVE-2021-43535",
      "initial_release_date": "2023-02-15T03:36:55Z",
      "product_status:known_not_affected": "168",
      "product_status:recommended": "2",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2021-43535",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2021-43535.json",
      "version": "19"
    }
  }
}



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Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.