CVE-2021-43535: debian debian_linux Use After Free
CVSS: 8.8v3.1HighModified
AliasesUBUNTU-CVE-2021-43535DEBIAN-CVE-2021-43535
Published 08-12-2021Last modified 04-08-2024
Vulnerability summary
CVE-2021-43535 is a high (CVSS 8.8) Use After Free vulnerability in debian debian_linux. EPSS estimates a 1.15% chance of exploitation in the next 30 days, higher than 66.2% of scored vulnerabilities.
CVSS score
8.8/10
010
High · v3.1 (NVD)EPSS score
1.15%
0%100%
Low · +0.04 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 15 · Related 1Timeline
- 08-12-2021PublishedVulnerability first disclosed.
- 04-08-2024Last modifiedVulnerability information updated.
Description
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.
CVSS metrics
4 scores · 3 sources · 2 versionsHigh 8.8Preferred score · NVD (NIST)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HSourcesAll 3 agree
- OSV · UbuntuEcosystem advisory · calculated8.8HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated8.8HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Medium 6.8Preferred score · NVD (NIST)
AV:N/AC:M/Au:N/C:P/I:P/A:PSourcesSingle source
EPSS trend
Probability
1.15%
Chance of exploitation in the next 30 days
Percentile
66%
Versus all other CVEs
30-day change
+0.04 pp
From 1.11% on 19-09-2026
19-09-202619-10-2026
EPSS score1.15%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian3 products
- firefox-esr< 91.3.0esr-1
- thunderbird< 1:91.3.0-1
- debian_linuxEOL9.0 | 10.0 | 11.0
Mozilla3 products
- firefox≥ unspecified, < 93 | < 93.0
- firefox_esr≥ unspecified, < 91.3 | < 91.3.0
- thunderbird≥ unspecified, < 91.3 | < 91.3.0
Ubuntu1 product
- thunderbird< 1:91.5.0+build1-0ubuntu0.18.04.1 | < 1:91.5.0+build1-0ubuntu0.20.04.1
3 vendors · 7 products
References
12 links- bugzilla.mozilla.org/show_bug.cgi?id=1667102X Refsource MISCREPORTIssue TrackingPermissions RequiredVendor Advisory
- lists.debian.org/debian-lts-announce/2021/12/msg00030.htmlMailing ListX Refsource MLISTThird Party Advisory
- www.debian.org/security/2022/dsa-5034Vendor AdvisoryX Refsource DEBIANIssue TrackingThird Party Advisory
- lists.debian.org/debian-lts-announce/2022/01/msg00001.htmlMailing ListX Refsource MLISTThird Party Advisory