Excelize: GetConditionalFormats indexes conditional-formatting rule sub-elements with no length or nil check

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Excelize is a Go language library for reading and writing Microsoft Excel spreadsheets. From 2.7.0 to 2.11.0, conditional-format extraction indexes required child slices or dereferences an optional colorScale child without validating malformed rule structure. GetConditionalFormats reaches extractCondFmtCellIs and also indexes ColorScale.Cfvo, DataBar.Cfvo, and DataBar.Color without complete structural checks. When a crafted worksheet supplies a cellIs, dataBar, or colorScale rule missing expected children and the application calls GetConditionalFormats, missing formula, color, value-object, or colorScale data reaches an out-of-range index or nil dereference, allowing an attacker to panic and terminate an unprotected process. No fixed version is available as of this review.

Source published

7 Oct 2026 18:45:20 UTC

Source modified

8 Oct 2026 16:09:37 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Excelize is a Go language library for reading and writing Microsoft Excel spreadsheets. From 2.7.0 to 2.11.0, conditional-format extraction indexes required child slices or dereferences an optional colorScale child without validating malformed rule structure. GetConditionalFormats reaches extractCondFmtCellIs and also indexes ColorScale.Cfvo, DataBar.Cfvo, and DataBar.Color without complete structural checks. When a crafted worksheet supplies a cellIs, dataBar, or colorScale rule missing expected children and the application calls GetConditionalFormats, missing formula, color, value-object, or colorScale data reaches an out-of-range index or nil dereference, allowing an attacker to panic and terminate an unprotected process. No fixed version is available as of this review.

Source published

Oct 7, 2026, 6:45:20 PM (timezone not stated)

Source modified

Oct 8, 2026, 4:09:37 PM (timezone not stated)

Observed here

9 Nov 2026 05:07:28 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Excelize is a Go language library for reading and writing Microsoft Excel spreadsheets. From 2.7.0 to 2.11.0, conditional-format extraction indexes required child slices or dereferences an optional colorScale child without validating malformed rule structure. GetConditionalFormats reaches extractCondFmtCellIs and also indexes ColorScale.Cfvo, DataBar.Cfvo, and DataBar.Color without complete structural checks. When a crafted worksheet supplies a cellIs, dataBar, or colorScale rule missing expected children and the application calls GetConditionalFormats, missing formula, color, value-object, or colorScale data reaches an out-of-range index or nil dereference, allowing an attacker to panic and terminate an unprotected process. No fixed version is available as of this review.

Source published

7 Oct 2026 19:17:34 UTC

Source modified

13 Oct 2026 14:18:54 UTC

Observed here

25 Oct 2026 04:17:41 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

## Summary `GetConditionalFormats` reads sub-elements of a `<cfRule>` straight out of `xl/worksheets/sheetN.xml` and indexes them without checking length, and in one case without checking for nil. Three rule types are affected: `cellIs`, `dataBar` and `colorScale`. A workbook with a rule that is missing a child a real Excel file would always have panics the call. ## Where it is All three sinks are in `styles.go`, at the same line numbers in v2.11.0 and on master `d552a7e`. All three are reached from `GetConditionalFormats` through `styles.go:3271`. `styles.go:3003`, in `extractCondFmtCellIs`: ```go format.Value = c.Formula[0] ``` The branch above it handles `len(c.Formula) == 2`; this one is the fallback and does not check that there is a formula at all, so a `cellIs` rule with no `<formula>` child indexes an empty slice. `styles.go:3132`, in the colorScale extractor: ```go values := len(c.ColorScale.Cfvo) ``` `c.ColorScale` is a `*xlsxColorScale` and is nil when the `<cfRule type="colorScale">` element has no `<colorScale>` child. Lines 3148 and 3153 then index `Cfvo[1]` and `Cfvo[2]` in the three-colour branch with no length check either. `styles.go:3186`, `:3188` and `:3190`, in the dataBar extractor: ```go format.MinType = c.DataBar.Cfvo[0].Type ... format.BarColor = "#" + f.getThemeColor(c.DataBar.Color[0]) ``` The guard here is `c.DataBar != nil`, which says nothing about the length of `Cfvo` or `Color`, so an empty `<dataBar></dataBar>` element reaches all three. ## Who the attacker is Anyone who can hand a spreadsheet to a service that opens it and calls `GetConditionalFormats`. No authentication, no user interaction beyond the service doing its normal job, and the file is small. ## Reproduction Three minimal `.xlsx` files were built, each a real zip with `[Content_Types].xml`, `_rels/.rels`, `xl/workbook.xml`, `xl/_rels/workbook.xml.rels` and one worksheet, opened each with the public `excelize.OpenReader` and called `GetConditionalFormats("Sheet1")`. Nothing internal is touched. The worksheet fragment for the `cellIs` case, note there is no `<formula>` child: ```xml <conditionalFormatting sqref="A1"><cfRule type="cellIs" operator="equal" priority="1" dxfId="0"/></conditionalFormatting> ``` for `dataBar`: ```xml <conditionalFormatting sqref="A1"><cfRule type="dataBar" priority="1"><dataBar></dataBar></cfRule></conditionalFormatting> ``` and for `colorScale`: ```xml <conditionalFormatting sqref="A1"><cfRule type="colorScale" priority="1"/></conditionalFormatting> ``` Observed against master `d552a7e` on go1.26.5: ```text cellIs panic: runtime error: index out of range [0] with length 0 styles.go:3003 styles.go:1217 styles.go:3271 dataBar panic: runtime error: index out of range [0] with length 0 styles.go:3186 styles.go:1262 styles.go:3271 colorScale panic: runtime error: invalid memory address or nil pointer dereference styles.go:3132 styles.go:1259 styles.go:3271 ``` One honesty note on impact. These are ordinary Go panics, not fatal errors, so a caller that wraps the call in `recover` survives them. ## Suggested fix Length-check `c.Formula` before line 3003 and return the rule with an empty value when there is no formula. Nil-check `c.ColorScale` before line 3132 and length-check `ColorScale.Cfvo` before indexing 1 and 2. Length-check `DataBar.Cfvo` and `DataBar.Color` alongside the existing nil check at 3186 to 3190. Skipping the malformed rule rather than erroring would keep `GetConditionalFormats` usable on files that are merely sloppy. ## Affected versions `github.com/xuri/excelize/v2` up to and including v2.11.0, and master at `d552a7e`. I read the three sinks at tag v2.11.0 and at master and ran the reproducers against master.

Source published

7 Oct 2026 20:22:54 UTC

Source modified

5 Nov 2026 23:25:39 UTC

Observed here

5 Nov 2026 23:38:32 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Publisher rating · MODERATE

GetConditionalFormats indexes conditional-formatting rule sub-elements with no length / nil check in github.com/xuri/excelize

Source published

5 Nov 2026 22:53:46 UTC

Source modified

5 Nov 2026 23:15:11 UTC

Observed here

5 Nov 2026 23:38:32 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.