CVE-2024-2961

What it actually does

CVE-2024-2961 is a buffer overflow in the GNU C Library iconv() implementation when converting data to the ISO-2022-CN-EXT character set. In affected glibc versions 2.39 and older, iconv() can write up to 4 bytes past the caller-provided output buffer. The immediate technical outcomes include application crashes, corruption of adjacent memory, and, in favorable conditions, limited overwrite of nearby variables or control-relevant data. Although the CVSS vector is local, the practical exposure depends on how applications expose character-set conversion: services that accept attacker-controlled text, encoding names, uploaded files, email content, web parameters, or document content and pass it to iconv() may create remotely reachable exploitation paths at the application layer. The issue has weaponized exploit maturity and a high EPSS score, indicating a meaningful likelihood of exploitation activity where reachable application patterns exist.

Why it matters to the business

Successful exploitation can disrupt applications that rely on glibc character conversion, causing service crashes, degraded availability, or instability in Linux-based platforms and appliances. In some application-specific circumstances, memory corruption may also enable limited data exposure or tampering. Because glibc is a foundational dependency across many Linux distributions and products, the affected footprint can be broad, including servers, containers, embedded appliances, storage/management platforms, and third-party products that bundle or depend on vulnerable glibc versions. The high EPSS score and weaponized exploit status increase urgency even though the vulnerability is not currently listed in CISA KEV and is not known from the provided data to be used in ransomware campaigns.

How an attack unfolds

An attacker first identifies an application or service that performs character-set conversion using glibc iconv(), especially one that allows the attacker to influence input text, uploaded content, document metadata, email content, HTTP parameters, or requested encodings. The attacker then supplies data that causes conversion to ISO-2022-CN-EXT. When the vulnerable iconv() path processes that data, glibc may write a small number of bytes beyond the allocated output buffer. In the simplest case, this corrupts heap or stack-adjacent data and crashes the process, producing a denial of service. In more advanced scenarios, the attacker repeatedly shapes input size, encoding state, allocation layout, and adjacent variables to turn the 4-byte overwrite into a controlled memory-corruption primitive. Real-world exploitability is highly dependent on the calling application, memory layout, runtime hardening, and whether the vulnerable conversion path is reachable from an untrusted input boundary.

How to fix it

Upgrade glibc through the operating system vendor’s security update channel to a version containing the fix for CVE-2024-2961. Because no universal fixed package versions were provided in the input, use the fixed glibc package version published by the relevant Linux distribution or product vendor for each affected platform. For Debian and other Linux distributions, apply the vendor security advisory updates rather than manually replacing glibc. For NetApp products and appliances listed as affected, follow NetApp product-specific advisories and firmware or software update guidance. Rebuild and redeploy containers, appliances, and statically packaged workloads that include vulnerable glibc-derived userlands; patching the host alone may not update vulnerable container images. Restart affected services after package updates so processes load the corrected libc. Where immediate patching is not possible, reduce exposure by disabling or restricting application features that allow untrusted users to select or trigger ISO-2022-CN-EXT conversion, validating or normalizing accepted character sets, blocking unexpected charset parameters at application gateways where safe, and isolating services that process untrusted text or files.

How to confirm the fix worked

Confirm exposure by inventorying systems and images for GNU glibc versions 2.39 and older and checking vendor security advisory status. On Linux systems, validate installed package versions using distribution package tools such as dpkg, rpm, apt, dnf, yum, or zypper, and confirm that the installed package changelog or advisory references the CVE fix. For containers, scan image layers for vulnerable glibc packages and rebuild from patched base images. Confirm remediation by restarting services and verifying running processes are mapped to the updated libc using tools such as lsof, /proc/<pid>/maps inspection, needrestart, checkrestart, or distribution-equivalent utilities. Application-level validation should include tests that exercise character conversion paths involving ISO-2022-CN-EXT and confirm they no longer crash or corrupt output. For vendor appliances, confirm the fixed firmware or software release is installed using the vendor management interface and advisory guidance.

Typical attack path

1. Find an application, service, batch processor, or appliance component running on affected glibc versions 2.39 or older.
2. Determine whether the component uses iconv() or a dependent library to convert attacker-controlled content or metadata between character sets.
3. Identify a path where conversion to ISO-2022-CN-EXT can be triggered directly or indirectly.
4. Send crafted input that exercises the vulnerable conversion routine and causes a small overwrite past the output buffer.
5. Observe process crashes, abnormal responses, worker restarts, or corrupted output to confirm reachability.
6. Refine payload length, encoding state, and request timing to achieve reliable denial of service or application-specific memory corruption.
7. If feasible, chain the memory corruption with knowledge of the target application and bypasses for platform protections to affect confidentiality, integrity, or availability.

How to detect it

Look for evidence that externally supplied content triggered unusual character conversion behavior, especially involving ISO-2022-CN-EXT. Relevant log sources include web server access logs, reverse proxy and WAF logs, application logs, mail gateway logs, document/file-processing service logs, crash reports, systemd journal entries, kernel logs, core dump metadata, EDR process telemetry, and container orchestrator restart events. Search for requests, uploaded content metadata, MIME headers, form fields, query parameters, API bodies, or error logs containing ISO-2022-CN-EXT or charset selection near the time of application crashes. Investigate repeated segmentation faults, aborts, worker process restarts, container CrashLoopBackOff events, or core dumps in services that process untrusted text, email, XML/HTML, PDFs, office documents, archives, or user uploads. Because exploitation is application-dependent and the overflow is small, there may be no universal network IOC beyond charset strings and crash artifacts. Correlate suspicious charset usage with process crashes, memory corruption messages, anomalous 5xx response spikes, and repeated requests from the same source. If core dumps are available, examine crashing stacks for iconv(), __gconv*, or ISO-2022-CN-EXT conversion routines and preserve samples for forensic review.

• ISO-2022-CN-EXT
• iso-2022-cn-ext
• charset=ISO-2022-CN-EXT
• charset="ISO-2022-CN-EXT"
• Content-Type: text/html; charset=ISO-2022-CN-EXT
• Content-Type: text/plain; charset=ISO-2022-CN-EXT
• iconv()
• iconv:
• gconv
• __gconv
• Segmentation fault
• segfault
• core dumped
• systemd-coredump
• CrashLoopBackOff
• /usr/lib/gconv/ISO-2022-CN-EXT.so
• /usr/lib64/gconv/ISO-2022-CN-EXT.so
• /lib/x86_64-linux-gnu/gconv/ISO-2022-CN-EXT.so

What your security team should do

• Prioritize patching internet-facing, file-processing, email-processing, web, API, document conversion, and identity/application gateway services that may process untrusted character-set input through glibc iconv().
• Treat this as high urgency because exploit maturity is weaponized and EPSS is high, even though it is not currently listed in CISA KEV.
• Inventory Linux servers, containers, virtual appliances, and affected third-party products for glibc versions 2.39 and older.
• Apply vendor glibc updates through supported OS channels and schedule service restarts or system reboots to ensure the patched library is in use.
• Rebuild and redeploy container images and application bundles that include their own glibc userland.
• Review applications and middleware for user-controlled charset conversion, especially support for ISO-2022-CN-EXT, and restrict unnecessary encodings where operationally feasible.
• Increase monitoring for crashes or repeated worker restarts in services that parse uploaded files, emails, web requests, or internationalized text.
• For NetApp and other vendor-managed products, follow product advisories and apply fixed firmware or software releases as they become available.