When trying to load a cross-origin resource in an audio/video context a decoding error may have resulted, and the content of that error may
When trying to load a cross-origin resource in an audio/video context a decoding error may have resulted, and the content of that error may have revealed information about the resource. This vulnerability affects Firefox < 86, Thunderbird < 78.8, and Firefox ESR < 78.8.
- DLA-2575-1
- DLA-2578-1
- DSA-4862-1
- DSA-4866-1
- openSUSE-SU-2021:0373-1
- openSUSE-SU-2021:0387-1
- RHSA-2021:0655
- RHSA-2021:0656
- RHSA-2021:0657
- RHSA-2021:0658
- RHSA-2021:0659
- RHSA-2021:0660
- RHSA-2021:0661
- RHSA-2021:0662
- SUSE-SU-2021:0659-1
- SUSE-SU-2021:0661-1
- SUSE-SU-2021:0667-1
- SUSE-SU-2021:0676-1
- SUSE-SU-2021:14657-1
- Published
- Feb 25, 2021
- Updated
- Jun 16, 2026
- EPSS
- 1.4% · 71th percentile
- CWE
- CWE-209
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Report tools
Action score
26
Monitor
Low priority for now.
- CVSS
- 26 / 40 · 6.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 1.4%
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| mozilla | firefox | cpe:2.3:a:mozilla:firefox |
| mozilla | firefox esr | cpe:2.3:a:mozilla:firefox_esr |
| mozilla | thunderbird | cpe:2.3:a:mozilla:thunderbird |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- debian debian linux10.0
- debian debian linux9.0
- mozilla firefoxbefore 86.0
- mozilla firefox esrbefore 78.8
- mozilla thunderbirdbefore 78.8
Versions reported by the vendor
Affected version ranges reported by the assigning authority (mozilla). Independent of NVD's CPE analysis and usually ahead of it.
Mozilla Firefox
- < 86affected
Mozilla Firefox ESR
- < 78.8affected
Mozilla Thunderbird
- < 78.8affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:10 | firefox-esr | before 78.8.0esr-1~deb10u1 | 78.8.0esr-1~deb10u1 |
| Debian:10 | thunderbird | before 1:78.8.0-1~deb10u1 | 1:78.8.0-1~deb10u1 |
| Debian:12 | firefox-esr | before 78.8.0esr-1 | 78.8.0esr-1 |
| Debian:12 | thunderbird | before 1:78.8.0-1 | 1:78.8.0-1 |
| Debian:9 | firefox-esr | before 78.8.0esr-1~deb9u1 | 78.8.0esr-1~deb9u1 |
| Debian:9 | thunderbird | before 1:78.8.0-1~deb9u1 | 1:78.8.0-1~deb9u1 |
| openSUSE:Leap 15.2 | MozillaFirefox | before 78.8.0-lp152.2.49.1 | 78.8.0-lp152.2.49.1 |
| openSUSE:Leap 15.2 | MozillaThunderbird | before 78.8.0-lp152.2.35.1 | 78.8.0-lp152.2.35.1 |
| Red Hat:enterprise_linux:7::client | firefox | before 0:78.8.0-1.el7_9 | 0:78.8.0-1.el7_9 |
| Red Hat:enterprise_linux:7::client | firefox-debuginfo | before 0:78.8.0-1.el7_9 | 0:78.8.0-1.el7_9 |
| Red Hat:enterprise_linux:7::client | thunderbird | before 0:78.8.0-1.el7_9 | 0:78.8.0-1.el7_9 |
| Red Hat:enterprise_linux:7::client | thunderbird-debuginfo | before 0:78.8.0-1.el7_9 | 0:78.8.0-1.el7_9 |
| Red Hat:enterprise_linux:8::appstream | firefox | before 0:78.8.0-1.el8_3 | 0:78.8.0-1.el8_3 |
| Red Hat:enterprise_linux:8::appstream | firefox-debuginfo | before 0:78.8.0-1.el8_3 | 0:78.8.0-1.el8_3 |
| Red Hat:enterprise_linux:8::appstream | firefox-debugsource | before 0:78.8.0-1.el8_3 | 0:78.8.0-1.el8_3 |
| Red Hat:enterprise_linux:8::appstream | thunderbird | before 0:78.8.0-1.el8_3 | 0:78.8.0-1.el8_3 |
| Red Hat:enterprise_linux:8::appstream | thunderbird-debuginfo | before 0:78.8.0-1.el8_3 | 0:78.8.0-1.el8_3 |
| Red Hat:enterprise_linux:8::appstream | thunderbird-debugsource | before 0:78.8.0-1.el8_3 | 0:78.8.0-1.el8_3 |
| Red Hat:rhel_eus:8.1::appstream | firefox | before 0:78.8.0-1.el8_1 | 0:78.8.0-1.el8_1 |
| Red Hat:rhel_eus:8.1::appstream | firefox-debuginfo | before 0:78.8.0-1.el8_1 | 0:78.8.0-1.el8_1 |
| Red Hat:rhel_eus:8.1::appstream | firefox-debugsource | before 0:78.8.0-1.el8_1 | 0:78.8.0-1.el8_1 |
| Red Hat:rhel_eus:8.1::appstream | thunderbird | before 0:78.8.0-1.el8_1 | 0:78.8.0-1.el8_1 |
| Red Hat:rhel_eus:8.1::appstream | thunderbird-debuginfo | before 0:78.8.0-1.el8_1 | 0:78.8.0-1.el8_1 |
| Red Hat:rhel_eus:8.1::appstream | thunderbird-debugsource | before 0:78.8.0-1.el8_1 | 0:78.8.0-1.el8_1 |
+11
Same product
mozilla: all recordsOther highest-scoring records for the same primary product.
- CVE-2010-3765Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before 3.1.6 and 3.0.x before 3.0.10, and SeaMonkey 2.x befKEV94Now
- CVE-2019-11708Insufficient vetting of parameters passed with the Prompt:Open IPC message between child and parent processes can result in the non-sandboxeKEV87Now
- CVE-2015-4495The PDF reader in Mozilla Firefox before 39.0.3, Firefox ESR 38.x before 38.1.1, and Firefox OS before 2.2 allows remote attackers to bypassKEV86Now
- CVE-2013-1690Mozilla Firefox before 22.0, Firefox ESR 17.x before 17.0.7, Thunderbird before 17.0.7, and Thunderbird ESR 17.x before 17.0.7 do not properKEV86Now
- CVE-2019-17026Incorrect alias information in IonMonkey JIT compiler for setting array elements could lead to a type confusion.KEV79This week
- CVE-2024-9680An attacker was able to achieve code execution in the content process by exploiting a use-after-free in Animation timelines.KEV76This week
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| debian:firefox-esr | 78.8.0esr-1 · Debian:12 | Package registry (OSV) |
| debian:thunderbird | 1:78.8.0-1 · Debian:12 | Package registry (OSV) |
| opensuse:MozillaFirefox | 78.8.0-lp152.2.49.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| opensuse:MozillaThunderbird | 78.8.0-lp152.2.35.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| red hat:firefox | 0:78.8.0-1.el8_3 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:firefox-debuginfo | 0:78.8.0-1.el8_3 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:firefox-debugsource | 0:78.8.0-1.el8_3 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:thunderbird | 0:78.8.0-1.el8_3 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:thunderbird-debuginfo | 0:78.8.0-1.el8_3 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:thunderbird-debugsource | 0:78.8.0-1.el8_3 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| suse:MozillaFirefox | 78.8.0-8.32.2 · SUSE:Linux Enterprise Module for Desktop Applications 15 SP2 | Package registry (OSV) |
| suse:MozillaThunderbird | 78.8.0-8.15.4 · SUSE:Linux Enterprise Workstation Extension 15 SP2 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- A user must open a link or visit a page.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- none
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- None
- Availability impact
- None
Weakness class (CWE)
CWE-209 · Generation of Error Message Containing Sensitive InformationCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- bugzilla.mozilla.org/show_bug.cgi?id=1690976
- lists.debian.org/debian-lts-announce/2021/03/msg00000.html
- security.gentoo.org/glsa/202104-09
- security.gentoo.org/glsa/202104-10
- www.debian.org/security/2021/dsa-4866
- www.mozilla.org/security/advisories/mfsa2021-07/
- www.mozilla.org/security/advisories/mfsa2021-08/
- www.mozilla.org/security/advisories/mfsa2021-09/
Vendor advisories and official records. Exploit/PoC links are deliberately left out.