CVE-2023-29552
CVE-2023-29552 is a security flaw in IETF Service Location Protocol (SLP). Attackers can make something fake look genuine in IETF Service Location Protocol (SLP). The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 8 Nov 2023.[1]
IETF Service Location Protocol (SLP) is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. IETF has published a fix or advice.
Description
CISA calls it a denial-of-service in IETF Service Location Protocol (SLP). In its words: “The Service Location Protocol (SLP) contains a denial-of-service (DoS) vulnerability that could allow an unauthenticated, remote attacker to register services and use spoofed UDP traffic to conduct a denial-of-service (DoS) attack with a significant amplification factor.”[1]
It scores 7.5 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; IETF’s advisory has them[3]. CISA names the product as IETF Service Location Protocol (SLP).
Most families won’t have IETF Service Location Protocol (SLP); it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 8 Nov 2023, 197 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 29 Nov 2023 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 64%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
IETF has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions or disable SLP service or port 427/UDP on all systems running on untrusted networks, including those directly connected to the Internet.”[1]
- Check whether you use it.IETF Service Location Protocol (SLP) is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 29 Nov 2023 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 7.5.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 64%.[4] |
See also
Other IETF flaws
- CVE-2023-44487, IETF HTTP/2: rapid reset attack ·
Similar flaws
- CVE-2026-118527, Ivanti Connect Secure: generation of predictable numbers or identifiers ·
- CVE-2026-46300, Linux Kernel: missing initialization of a variable ·
- CVE-2026-41709, Broadcom VMware ESX: insufficient logging ·
- CVE-2026-96656, Plex Media Server: external control of file name or path ·
- CVE-2026-96654, Plex Media Server: improper neutralization of encoded URI schemes in a web page ·
References
- ^ Cybersecurity and Infrastructure Security Agency. “Service Location Protocol (SLP) Denial-of-Service Vulnerability”. Known Exploited Vulnerabilities Catalog, added 8 Nov 2023.
- ^ National Institute of Standards and Technology. “CVE-2023-29552 Detail”. National Vulnerability Database, published 25 Apr 2023.
- ^ IETF. Advisories and fixes: bitsight.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.640, percentile 99.2, 31 Oct 2026.
- CVE Program. “CVE-2023-29552”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.