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NVD / CVE Program· CNA mitre

CVE-2020-28361: Kamailio before 5.4.0, as used in Sip Express Router (SER) in Sippy Softswitch 4.5 through 5.2 and other products, allows a bypass of a head

Noroxi assessment

Priority: Monitor (action score 21/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.1% (FIRST EPSS); higher than 66.1% of all records.
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: kamailio (Debian:12) 5.4.0-1.

Low priority for now. Upgrade to kamailio (Debian:12) 5.4.0-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Kamailio before 5.4.0, as used in Sip Express Router (SER) in Sippy Softswitch 4.5 through 5.2 and other products, allows a bypass of a header-removal protection mechanism via whitespace characters. This occurs in the remove_hf function in the Kamailio textops module. Particular use of remove_hf in Sippy Softswitch may allow skilled attacker having a valid credential in the system to disrupt internal call start/duration accounting mechanisms leading potentially to a loss of revenue.

MediumCVSS 5.4 · v3.1—No exploit Fix available
Published
Nov 18, 2020
Updated
Jun 16, 2026
EPSS
1.1% · 66th percentile

Report tools

JSON

Action score

21

Monitor

Low priority for now.

CVSS
21 / 40 · 5.4 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.1%

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
kamailiokamailio

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • kamailio kamailiobefore 5.4.0

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12kamailiobefore 5.4.0-15.4.0-1

Same product

kamailio: all records

Other highest-scoring records for the same primary product.

  • CVE-2018-14767In Kamailio before 5.0.7 and 5.1.x before 5.1.4, a crafted SIP message with a double "To" header and an empty "To" tag causes a segmentation
    48Plan
  • CVE-2018-8828A Buffer Overflow issue was discovered in Kamailio before 4.4.7, 5.0.x before 5.0.6, and 5.1.x before 5.1.2.
    48Plan
  • CVE-2016-2385Heap-based buffer overflow in the encode_msg function in encode_msg.c in the SEAS module in Kamailio (formerly OpenSER and SER) before 4.3.5
    48Plan

Published before and after this one in the same product

  • ← EarlierCVE-2015-1590Sep 7, 2017 · The kamcmd administrative utility and default configuration in kamailio before 4.3.0 use /tmp/kamailio_ctl.
    31Monitor
  • ← EarlierCVE-2018-16657Sep 7, 2018 · In Kamailio before 5.0.7 and 5.1.x before 5.1.4, a crafted SIP message with an invalid Via header causes a segmentation fault and crashes Ka
    40Plan
  • Later →CVE-2020-27507Mar 15, 2023 · The Kamailio SIP before 5.5.0 server mishandles INVITE requests with duplicated fields and overlength tag, leading to a buffer overflow that
    39Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:kamailio5.4.0-1 · Debian:12Package 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.

No history yet (it accumulates with the daily EPSS job).

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 researchers

Finders, 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.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/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.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records