CVE-2024-2608 Overview
CVE-2024-2608 is an integer overflow vulnerability affecting Mozilla Firefox, Firefox ESR, and Thunderbird. The flaw resides in the AppendEncodedAttributeValue(), ExtraSpaceNeededForAttrEncoding(), and AppendEncodedCharacters() functions. Integer overflows during size calculations cause underallocation of an output buffer, which produces an out-of-bounds write [CWE-680]. Attackers exploiting the condition can corrupt adjacent memory and potentially achieve code execution within the browser process. The vulnerability affects Firefox versions before 124, Firefox ESR before 115.9, and Thunderbird before 115.9.
Critical Impact
Successful exploitation can lead to memory corruption and arbitrary code execution in the context of the affected browser or mail client, compromising confidentiality, integrity, and availability of the host.
Affected Products
- Mozilla Firefox versions prior to 124
- Mozilla Firefox ESR versions prior to 115.9
- Mozilla Thunderbird versions prior to 115.9 (and Debian Linux 10 packages)
Discovery Timeline
- 2024-03-19 - CVE-2024-2608 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-2608
Vulnerability Analysis
The vulnerability is an integer overflow to buffer overflow [CWE-680] within Mozilla's HTML/XML attribute encoding logic. Three related routines participate in the flaw: ExtraSpaceNeededForAttrEncoding() calculates how many additional bytes are needed to hold an encoded attribute value, while AppendEncodedAttributeValue() and AppendEncodedCharacters() perform the actual write into the destination buffer.
When the source content is large enough, the arithmetic used to compute the required buffer size wraps around a fixed-width integer. The caller then allocates a buffer smaller than the encoded output actually requires. When the encoder writes character replacements such as &, ", or &#xNN; into the undersized buffer, it writes past the allocation.
Exploitation requires attacker-controlled content to be processed by the encoding path, which is reachable through crafted web pages or HTML email messages rendered by Thunderbird.
Root Cause
The root cause is unchecked integer arithmetic when computing the output size for attribute and character encoding. Multiplying or adding per-character expansion factors against large input lengths overflows before the size is passed to the allocator, producing an undersized destination for the subsequent write loop.
Attack Vector
The attack vector is local per the CVSS metrics, but the vulnerable code is reached by rendering attacker-controlled markup. A victim visiting a malicious page in Firefox or opening a crafted HTML message in Thunderbird triggers the encoding path with content sized to induce the overflow.
No public proof-of-concept exploit has been published, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Because verified proof-of-concept code is not available, this article does not include exploitation code. See the Mozilla Bug Report #1880692 for the internal analysis.
Detection Methods for CVE-2024-2608
Indicators of Compromise
- Unexpected Firefox, firefox-esr, or Thunderbird process crashes with heap corruption signatures in crash reports or about:crashes telemetry.
- Child content processes spawning unexpected shells (cmd.exe, powershell.exe, /bin/sh) or writing executables to user-writable paths.
- Outbound connections from firefox.exe or thunderbird.exe to newly registered or low-reputation domains shortly after rendering untrusted HTML content.
Detection Strategies
- Inventory endpoints for Firefox versions below 124, Firefox ESR below 115.9, and Thunderbird below 115.9 using software asset management or EDR telemetry.
- Alert on browser or mail-client processes performing anomalous post-render behavior such as memory-region protection changes, module injection, or child-process creation.
- Correlate crash-dump telemetry indicating heap-buffer-overflow annotations with the affected binaries.
Monitoring Recommendations
- Ingest browser and mail-client crash telemetry into your SIEM or data lake for centralized triage.
- Track patch-compliance metrics for Mozilla products alongside other high-severity third-party software.
- Monitor DNS and proxy logs for browser-originated requests to known exploit-delivery infrastructure and newly seen domains.
How to Mitigate CVE-2024-2608
Immediate Actions Required
- Update Firefox to version 124 or later on all managed endpoints.
- Update Firefox ESR to 115.9 or later where extended-support builds are deployed.
- Update Thunderbird to 115.9 or later, including on Debian Linux systems via the vendor-supplied package.
- Restart the browser and mail client after patching so the new binaries are loaded into memory.
Patch Information
Mozilla addressed the flaw in Firefox 124, Firefox ESR 115.9, and Thunderbird 115.9. Details are published in Mozilla Security Advisory MFSA-2024-12, MFSA-2024-13, and MFSA-2024-14. Debian Linux users should apply the updates described in Debian LTS Announcement #22 and Debian LTS Announcement #28.
Workarounds
- Disable rendering of remote HTML content in Thunderbird until the client is upgraded.
- Restrict browsing to trusted destinations through enterprise web filtering while patches are being deployed.
- Enforce least-privilege user accounts so a successful browser compromise does not yield administrative rights on the host.
# Confirm patched versions on Linux endpoints
firefox --version
firefox-esr --version
thunderbird --version
# Debian package update example
sudo apt-get update && sudo apt-get install --only-upgrade firefox-esr thunderbird
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
