Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Attack requirements (AT:N) | No attack requirements |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Confidentiality (VC:N) | No confidentiality impact |
| Integrity (VI:N) | No integrity impact |
| Availability (VA:H) | High availability impact |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
About Pjsip
CVE-2026-28799 affects Pjsip, a product from Pjsip. Before acting, confirm where Pjsip runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: PJSIP is a free and open source multimedia communication library written in C. Prior to version 2.17, a heap use-after-free vulnerability exists in PJSIP's event subscription framework (evsub.c) that is triggered during presence unsubscription (SUBSCRIBE with Expires=0). This issue has been patched in version 2.17.
The weakness class is Use After Free. Memory is used after it was released, which can lead to code execution.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Pjsip |
| Affected versions | Pjsip before 2.17 |
| Published | Mar 6, 2026 |
| Last modified | Jun 17, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | security-advisories@github.com |
How to detect it
- Inventory every instance of Pjsip and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Pjsip named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Pjsip to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-416: Use After Free More CVEs with this weakness
Technical References
Frequently asked questions
Related CVEs
PJSIP is a free and open source multimedia communication library written in C. In 2.16 and earlier, a stack buffer overflow exists in pjsip_auth_create_digest2() in PJSIP when using pre-computed digest credentials (PJSIP_CRED_DATA_DIGEST). The function copies credential data using cred_info->data.slen as the length without an upper-bound check, which can overflow the fixed-size ha1 stack buffer (128 bytes) if data.slen exceeds the expected digest string length.
PJSIP is a free and open source multimedia communication library written in C. In 2.16 and earlier, there is a buffer overflow when decoding Opus audio frames due to insufficient buffer size validation in the Opus codec decode path. The FEC decode buffers (dec_frame[].buf) were allocated based on a PCM-derived formula: (sample_rate/1000) * 60 * channel_cnt * 2. At 8 kHz mono this yields only 960 bytes, but codec_parse() can output encoded frames up to MAX_ENCODED_PACKET_SIZE (1280) bytes via opus_repacketizer_out_range(). The three pj_memcpy() calls in codec_decode() copied input->size bytes without bounds checking, causing a heap buffer overflow.
PJSIP is a free and open source multimedia communication library written in C. Versions 2.16 and below have a Heap-based Buffer Overflowvulnerability in the DNS parser's name length handler. Thisimpacts applications using PJSIP's built-in DNS resolver, such as those configured with pjsua_config.nameserver or UaConfig.nameserver in PJSUA/PJSUA2. It does not affect users who rely on the OS resolver (e.g., getaddrinfo()) by not configuring a nameserver, or those using an external resolver via pjsip_resolver_set_ext_resolver(). This issue is fixed in version 2.17. For users unable to upgrade, a workaround is to disable DNS resolution in the PJSIP config (by setting nameserver_count to zero) or to use an external resolver implementation instead.
PJSIP is a free and open source multimedia communication library written in C. Versions 2.16 and below contain a heap use-after-free vulnerability in the ICE session that occurs when there are race conditions between session destruction and the callbacks. This issue has been fixed in version 2.17.
PJSIP is a free and open source multimedia communication library written in C. Prior to version 2.17, there is a stack buffer overflow vulnerability when pjmedia-codec parses an RTP payload contain more frames than the caller-provided frames can hold. This issue has been patched in version 2.17.
PJSIP is a free and open source multimedia communication library written in C. In 2.16 and earlier, a buffer overflow vulnerability exists in PJNATH ICE Session when processing credentials with excessively long usernames.
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