CVE-2021-40438
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mod_proxy SSRF
rank 79 = 40 + 23 + 0 + 10 + 6
rank@v1 · act now
Someone is already using it
CISA KEV catalog · public proof-of-concept · FIRST EPSS
EPSS 0.99999 · CISA KEV listed · without this subject the record ranks 39
What it costs you if it fires
NVD CVSS base score, then the CNA's own
CVSS 9.0, from NVD · without this subject the record ranks 56
It is getting worse, not staying still
FIRST EPSS series, rescorings and bad loads removed
no persisting rise in 365 days · without this subject the record ranks 79
How much of the world it touches
NVD CPE configurations
20 products in the CPE ranges · without this subject the record ranks 69
Someone else already set the date
CISA KEV remediation due date
CISA remediation date held · without this subject the record ranks 73
$4.99M = $4.99M incident cost x 1 exposure x 0.99999 likelihood
udv@v1 · unaudited · wrong for you until you say what you run
$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.
Hindsight · the state
Foresight · where to check next
This record is one instance of CWE-918, server-side request forgery (ssrf). The index holds 3591 prior instances of this class, 23 KEV-listed. The nearest of its KEV-listed records are drawn beside this. taxonomy@v1
Running Apache HTTP Server? Check your version
A deterministic range check against the ranges this record publishes. It tells you where a version sits in the record, not whether your deployment is exploitable. No account needed.
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Matches your own product list against every record this index holds, and tells you when one of them moves.
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Harm, if it fires from the vector and the weakness
Written for the ticket you're about to file.
CISA KEV & Federal Remediation Deadline from the record and CISA
The fix, and how long it's been waiting.
Exploit Status & Known PoCs a ladder, not a score
Current rung: Ransomware campaign use known, 2021-12-01.
Affected & Fixed Versions as published
Show all 20 published ranges
A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.
What it is stated by the CNA
A crafted request uri-path can cause mod_proxy to forward the request to an origin server choosen by the remote user. This issue affects Apache HTTP Server 2.4.48 and earlier. receipt
NVD's analysis a second authority
- severity
- 9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- weakness
- CWE-918
- affected versions
- resf rocky linux 8.0; redhat enterprise linux 8.0; redhat enterprise linux eus 8.1; and 17 more, listed in full below
- also scored by
- 9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
check it yourself httpd.apache.org lists.fedoraproject.org lists.apache.org lists.apache.org lists.apache.org lists.apache.org +13 morereceipt
Dated events
Movement the material steps
This score more than doubled inside 72 hours. Both observations are in the full history below.
Show all 63 observations
63 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt
The full biography
Listed by CISA 76 days after it published, exploit probability more than doubled between 2021-09-21 and 2021-09-24 (0.00785 → 0.01823) and the record had been public for 4 years, 11 months when this index was last written.
No material movement in 81 days as of the last ingest this index recorded.
The pattern, elsewhere
This record is one instance of CWE-918, server-side request forgery (ssrf). The index holds 3591 prior instances of this class, 23 KEV-listed. The nearest of its KEV-listed records are drawn beside this. [email protected]
"Matches n of m" counts the attributes the two records can both be compared on: the CVSS metrics they share a version of, any weakness class beyond this one, and the vendor. fit-rules@v1
3591 records in this class held. The six above are drawn from the ones CISA has listed as exploited, ranked by how much of the record matches this one. That is why every one of them is KEV-listed: the pool is, so the colour on those spokes says nothing the pool has not already said.
No curated product neighbourhood is held for this product, so the records above are the nearest this index can name. The neighbourhood table covers a small set of products and is extended by hand.
Siblings and hubs
Records related to this one
Its defect family
apache software foundation apache http server
Of the 6 records in this family, this is the only one with public proof-of-concept code, and it holds 10 references to it.
Grouped by shared product and weakness, not by shared vulnerability. Each record's own state is on its own page.
Family membership: held values
This record is one of a group, and the group's page describes all of them. This page is kept and dated, and the defect family's own page is the one we offer for indexing: the whole group.
Browse the index from here
These are index-wide views, not findings about CVE-2021-40438.
What usually comes next
Everything above needs no account. What is below is work: assembling it, scoping it to your estate, watching it, and handing it to someone else.